US7583229B2 - Method for detection of faulty antenna array elements - Google Patents
Method for detection of faulty antenna array elements Download PDFInfo
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- US7583229B2 US7583229B2 US11/659,772 US65977206A US7583229B2 US 7583229 B2 US7583229 B2 US 7583229B2 US 65977206 A US65977206 A US 65977206A US 7583229 B2 US7583229 B2 US 7583229B2
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- antenna array
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/267—Phased-array testing or checking devices
Definitions
- This invention relates to detection of faulty antenna array elements and more particularly to a method for determining faulty unterminated elements in the antenna array.
- Antenna arrays having multiple elements have been used extensively in direction-finding in which the direction of the major lobe of the array, as well as the side lobe configuration, is determined by a number of active and passive elements in the array.
- the array assembly is first manufactured and then located in a housing commensurate with the application.
- the antenna array is housed in pods or in Fiberglas housings, which are then deployed on the aircraft.
- the active elements of the array their proper operation can be tested by cabling the active elements to a back plane where the standing wave ratio of the active elements can be ascertained in a conventional manner.
- proper operation of such an array can be ascertained in the far field by mounting the antenna array at the center of a rather large antenna range and detecting the radiation pattern. This is effective to ascertain if the radiation pattern matches the desired radiation pattern, but in no way indicates what element or elements are faulty in the array.
- transporting an antenna to a facility is uneconomical at best and impractical in most instances because, for instance, if antenna arrays are to be mass-produced at 10 per day, it would be impractical to transport the antenna arrays to an antenna range that may be some miles from the manufacturing facility.
- the passive elements which are terminated in most cases by a 50-ohm resistor at the input to the passive element.
- the passive elements could be Vivaldi notch antennas, dipoles, monopoles or V antennas; or in fact any convenient antenna configuration.
- microwave antennas are terminated with chip-type surface mount resistors that are soldered onto the antenna adjacent the feedpoint.
- This method of fabricating antenna arrays is not easily checked after manufacture other than by transporting the finished antenna array to the antenna range, of which there are very few in existence.
- the task is to obtain the antenna arrays coming off the production line and to rapidly test them before they go onto the next step, which involves embedding the array into a structure to be mounted for a particular application.
- the task is to make sure that the antenna array is working properly before other production processes take place, such as, for instance, delivery for integration into whatever platform they are to be used in. If one were to be able to test the array and find out if there is a problem, the problem could be repaired prior to integration. However, if one waited until after integration, if the antenna array proved defective it could not be readily repaired.
- antenna arrays in general for direction-finding purposes include tapered blades, standard dipoles or broadband monopoles or dipoles, and it is an urgent matter to be able to test them bare. Once they get wrapped in Fiberglas for anti-ice protection and the like, they cannot be readily fixed.
- the subject method or system provides a convenient way to test an assembled antenna array right on the production floor. Not only can the existence of a defective antenna array be ascertained immediately, but also what elements in the array are unterminated and therefore causing a distorted antenna pattern.
- the method in general includes testing the antenna array by irradiating it with pulses from one or more transmit/receive antennas and measuring the absorption of the impinging energy by the terminated antenna elements. If the elements are properly terminated, then the passive element absorbs energy, which results in reduced energy reflected back to the transmit/receive antennas. What the system is testing is the degree to which a passive element is absorbing energy.
- the returned signals are passed through a frequency domain reflectometer and the output of the reflectometer for the antenna under test is cross-correlated with a large number of so-called contingency templates.
- contingency templates are generated from the measured results from altering an ideal gold standard array by purposely unterminating various elements.
- the contingency templates are generated using a gold standard or perfect antenna and purposely unterminating various of the passive elements of the gold standard array. This provides a large number of contingency templates one-to-one correlatable with the passive element or elements that are unterminated.
- this is done on the plant floor by locating a number of transmit/receive antennas spaced, for instance, two feet apart and directed towards the antenna array under test, which in one embodiment is eight feet from these transmit/receive antennas.
- the transmit/receive antennas are driven in sequence by a transmitter, with the results multiplexed to a frequency domain reflectometer that is used because its reflection coefficient output reflects both the phase and amplitude of the reflected signals.
- the frequency domain reflectometer is used to provide more information than would be available from a time domain reflectometer.
- the antenna array under test is placed in an anechoic chamber to minimize reflections from artifacts within the chamber or from the chamber walls themselves. Since the test signals projected by the transmit/receive antennas have a pulse repetition rate, time gating is utilized to eliminate returns from the irradiated antenna array that are the result of multi-path, thereby to eliminate corruption of the reflection coefficient signals from the frequency domain reflectometer.
- a template having a 2-D vector configuration is generated using the outputs of the three transmit/receive antennas.
- 10,000 templates are generated corresponding to the 10,000 contingencies that would result from, for instance, all permutations and combinations of three unterminated elements in, for instance, a ten-element array.
- the contingency templates utilize the gold standard vector template to normalize all measurements. Moreover, the gold standard vector template is also utilized to analyze the antenna array under test so as to generate a TEST vector to be cross-correlated against all of the contingency vector templates.
- the spacing is such as to be able to intercept the main lobe of the antenna array so that effective measurements can be made of the antenna under test.
- the antenna array under test is compared with a gold standard antenna array that has been purposely altered to unterminate various combinations of its passive elements to establish all possible contingencies for the array. All testing is done in accordance with a gold standard antenna array, with the contingency templates generated by altering the gold standard antenna through unterminating various of the passive elements.
- a frequency domain reflectometer is used to generate all the reflection coefficients used, with cross-correlation of reflection coefficients with a complete set of contingency templates permitting identifying unterminated passive array elements.
- FIG. 1 is a diagrammatic illustration of an antenna array having passive and active elements, which produces an ideal antenna pattern, with the array forming the gold standard for measurement purposes;
- FIG. 2 is a diagrammatic illustration of the distortion of the antenna pattern of FIG. 1 given a defective unterminated element of the antenna array of FIG. 1 ;
- FIG. 3 is a diagrammatic illustration of the utilization of a gold standard and a contingency array in a test environment in which a transmitter transmits pulses from a transmit/receive antenna to the array and in which reflected energy is analyzed by a frequency domain reflectometer that provides reflection coefficients to a gold standard vector generator outputted to a contingency template generator for generating a large number of contingency vector templates corresponding to the contingencies that would be expected with an array having one or more unterminated elements;
- FIG. 4 is a diagrammatic illustration of the testing of an antenna array having unterminated elements in which returns from the antenna array under test are processed by the frequency domain reflectometer of FIG. 3 so as to generate a TEST vector for the antenna under test, which TEST vector is cross-correlated with contingency vector templates to ascertain via correlation coefficient and thresholding the identity of the matching contingency and therefore the identity of the defective array element or elements;
- FIG. 5 is a diagrammatic illustration of the utilization of multiple transmit and receive antennas and the generation of reflection coefficients for outputs from the three antennas;
- FIG. 6 is a diagrammatic illustration of a contingency in which one of the elements of the array is unterminated so as to generate a series of reflection coefficients corresponding to the receipt of reflected signals at the transmit/receive antennas;
- FIG. 7 is a series of equations utilized to create a template for the contingency of FIG. 6 in which templates for the three antennas are derived from the measured reflection coefficients for the contingency of FIG. 6 , divided by gold standard reflection coefficients for the indicated transmit/receive antenna;
- FIG. 8 is a diagrammatic illustration of the creation of a 2-D vector template utilizing the templates associated with each of the transmit/receive antennas to create a number N of T 2-D C N templates that characterize every contingency for the array;
- FIG. 9 is a diagrammatic illustration of the process of testing an antenna to create a 2-D TEST vector for the antenna array under test by measuring the reflection coefficients for the antenna array under test at each of the transmit/receive antennas, developing a test vector for each of the measured readings normalized to the gold standard reflection coefficients and the utilization of the test vectors for each of the transmit/receive antennas in a 2-D TEST A vector to fully characterize the characteristics of the antenna under test;
- FIG. 10 is a diagrammatic illustration of the calculation of the correlation coefficient for all contingencies based on the 2-D templates for all of the contingencies, which are dot-multiplied by the 2-D Test A vector divided by the absolute magnitude of the 2-D contingency templates multiplied by the absolute magnitude of the 2-D TEST A vector;
- FIG. 11 is a graph showing probability density versus probability, showing two populations that are the result of the correlation of FIG. 10 , illustrating an area for which there are no defects, a correlation coefficient threshold and a population showing a defect as determined by correlation between the reflection coefficients of the antenna array dot-multiplied by the contingency templates to indicate that one contingency template is highly correlated;
- FIG. 12 is a chart illustrating the ranking of the various defects corresponding to the contingency templates, illustrating the rank of cross-correlations for all of the contingency templates, whereby through analysis of the rank and the distance of the defect from the next adjacent rank, one can ascertain the unterminated element or elements corresponding to the K contingency; and,
- FIG. 13 is a diagrammatic illustration of the sequencing of pulses from a transmitter through various transmit/receive antennas, also indicating time gating to eliminate from frequency domain reflectometer measurements artifacts or multi-path returns that exist at the apertures of the transmit/receive antennas.
- the ideal antenna array in order to test a multi-element antenna array 10 having an active element 12 and passive elements 14 , 16 , 18 , 20 and 22 , the ideal antenna array, hereinafter called the gold standard, produces an ideal antenna pattern 24 having a major lobe 26 and various side lobes 28 , all symmetrical about the center line 30 of the array.
- This ideal antenna pattern permits direction-finding applications in which the direction of incoming signals is determined through the directionality of the antenna array.
- antenna array 10 has a defective passive element 20 due to the fact, for instance, that the element is unterminated and therefore does not absorb incoming radiation
- the entire array will have a distorted antenna pattern, here illustrated at 32 , in which at the very least the axis of the major lobe 26 ′, namely axis 30 ′, is considerably altered with respect to the ideal axis as illustrated in FIG. 1 .
- FIG. 3 it is the purpose of the subject invention to irradiate or illuminate a gold standard array or a contingency array 10 with radiation from one or more antennas 40 that are driven by a transmitter 42 with pulses 44 that are projected towards the array.
- the transmit/receive antenna 40 transmits the outgoing pulses and receives the reflected pulses, here illustrated at 46 , and couples them through a circulator 48 to a receiver 50 that is in turn coupled to a frequency domain reflectometer 52 .
- the output of the frequency domain reflectometer is a reflection coefficient, here designated S 11 .
- the output of frequency domain reflectometer 52 is coupled to a module 54 that generates a gold standard vector composed of a number of reflection coefficients for the transmit/receive antenna over a band of frequencies ⁇ .
- the gold standard vector be it a 1-D or 2-D vector, which is utilized to normalize the measurements.
- the gold standard array 10 is purposely altered by unterminating selected passive elements, as illustrated at 56 , it being understood that it is necessary to provide for a large number of contingencies. For instance, in an 11-element array that has, for instance, 10 passive elements, if only one element is determined to be unterminated, then there is one position in ten for which a contingency template must be made. If one considers the possibility that there are, in any given array under test, 2 unterminated elements, then this multiplies the numbers of contingency templates that must be generated. Likewise, when considering potentially 3 unterminated elements, the number of contingency templates can be as high as, for instance, 10,000.
- this step it is the purpose of this step to generate contingency templates, as illustrated at 60 , by outputting the frequency domain reflectometer reflection coefficients for each of the contingencies. This requires each of the contingency arrays to have a different unterminated element or elements, so as to generate a number of contingency vector templates 62 .
- the reflection coefficients have both phase and amplitude values, and these phase and amplitude values are contained in the contingency vector template for each of the contingencies, again based on the gold standard or ideal antenna.
- time domain reflectometer in place of a frequency domain reflectometer in order to detect the reflections from the illuminated antenna array and to take only those reflections that come in at a predetermined time period so as to eliminate multi-path and other artifacts.
- time gate a time domain reflectometer to eliminate responses of the transmit/receive antenna from other things happening inside the chamber, such as reflections off the chamber walls.
- time gating to isolate the response of the antenna being radiated, a opposed to artifacts.
- time gating will be discussed hereinafter, for purposes of discussion it will be appreciated that one cannot narrowly define a time gate window to provide an output pulse envelope that is sufficiently narrow to be able to detect what is happening at each of the individual elements of the array. Thus, if one uses a time domain reflectometer, one cannot know which of the elements is bad and which of the elements are good.
- time domain reflectometry When utilizing time domain reflectometry, one is not able to detect the missing element by simply looking at the shape of the pulse that comes back to the transmit/receive antenna. In other words, time domain reflectometry is an extremely insensitive procedure.
- phase and amplitude are detected in order to be able to determine unterminated or malfunctioning elements.
- symbol S 11 refers to the complex reflection coefficient.
- an antenna array under test 66 may, for instance, have a number of unterminated elements, here illustrated at 68 .
- transmitter 42 illuminates the antenna array under test with pulse 44 and receives reflected pulses 46 , these pulses are detected by receiver 50 and are coupled to frequency domain reflectometer 52 as described above.
- the complex reflection coefficients from the frequency domain reflectometer are both coupled to the module 54 , which generates the gold standard vector, and are also applied to a module 70 that generates an antenna-under-test vector.
- the antenna-under-test vector is normalized utilizing the output from module 54 so as to provide a normalized test vector 72 that is dot-multiplied with all of the contingency vector templates, here illustrated at 74 .
- the cross-correlation is illustrated in dotted box 76 , with the correlation coefficients being thresholded at 78 and/or provided to a module that ranks the correlation coefficients, here illustrated at 80 .
- the correlation coefficients being thresholded at 78 and/or provided to a module that ranks the correlation coefficients, here illustrated at 80 .
- one identifies the matching contingency and therefore the corresponding configuration of the antenna, as illustrated at 82 .
- This subsequently results in the identification of the defective array element, as illustrated at 84 .
- the identification occurs by merely noting which of the contingency configurations has the highest cross-correlation coefficient and noting for the contingency which of the antenna array elements of the antenna array under test have unterminated outputs or apertures.
- Antenna # 1 a number of transmit/receive antennas, here illustrated by Antenna # 1 , Antenna # 2 and Antenna # 3 , each of which illuminate an element 90 on array 10 from three different directions, namely 92 , 94 and 96 .
- the outputs of these antennas when operating in the receive mode are coupled to respective frequency domain reflectometers 98 , 100 and 102 that again respectively output complex reflection coefficients (S 11 ) ANT1 , (S 11 ) ANT2 and (S 11 ) ANT3 .
- the purpose of using multiple antennas is to provide more information such that the measurements are, for instance, three times the size of those from a single antenna. It is noted also that the use of multiple antennas significantly decreases the false alarm rate if one is looking for unterminated antenna elements because the larger the template that can be generated, whether it be for the gold standard, the contingency templates, or the antenna-under-test vector, the less the false alarm rate will be due the higher probability of detection.
- the gold standard antenna must be reconfigured for each of the possible unterminated antenna element contingencies that might happen.
- a Contingency 1 is illustrated in which the gold standard array has one of its elements unterminated, as illustrated at 108 .
- TEST For an antenna under test, one must create a 2-D vector, here designated as TEST.
- TEST In order to test the antenna array, one measures for each of the transmit/receive antennas the complex reflection coefficient for the test antenna array, with the antenna array under test designated A.
- test vectors namely TEST A ANT1 , TEST A ANT2 and TEST A ANT3 . Again, these measurements are normalized to the gold standard reflection coefficients for each of the transmit/receive antennas.
- TEST A ANT1 , TEST A ANT2 and TEST A ANT3 reflection coefficients are then used to develop a 2-D TEST A vector so as to fully characterize the antenna array under test.
- the correlation coefficient is the dot-product of all of the contingency templates in 2-D form, dot-multiplied by the complex conjugate of the 2-D TEST vector for the antenna array under test, all divided by the multiplication of the absolute magnitude of the N 2-D templates multiplied by the absolute magnitude of the 2-D TEST A vector.
- FIG. 11 is a graph of probability density versus probability that has two populations, illustrated by curve 120 .
- the first population which lies to the left of a probability threshold 122 , indicates that for all of the contingencies there is no high correlation, therefore no defect.
- the ranking system may be used because one can immediately compare by rank all of the contingencies and ascertain if there is one contingency that has a correlation coefficient that is much larger than any of the rest. This in turn permits another means of identifying the contingency that has the high correlation and thus the defect and the corresponding unterminated element or elements.
- an antenna array 130 is usually placed in an anechoic chamber 132 and is spaced from the transmit/receive antennas Numbers 1 , 2 and 3 , which are in turn coupled to circulators 134 , 136 and 138 respectively.
- Transmitter 140 produces pulses that are sequentially coupled to the transmit/receive antennas via a single-pole, multiple-throw switch 142 that is under the control of a control unit 144 .
- What is therefore provided is a method for locally testing bare antennas as they come off the production line to ascertain if any of the passive elements are unterminated and to be able to correct the defective elements by properly terminating them prior to their being encapsulated or deployed in their particular application. This saves considerable amount of time and considerable expense so that the individual bare antennas need not be transported to a large antenna range for testing. The result is enhanced quality control for antenna arrays produced on a production line and minimizes expense.
- the subject system solves the problem of ascertaining not only that the antenna pattern for a particular array under test is defective, but also to ascertain what passive elements in the array are causing the problem.
Abstract
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US11/659,772 US7583229B2 (en) | 2005-02-24 | 2006-02-24 | Method for detection of faulty antenna array elements |
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US65578405P | 2005-02-24 | 2005-02-24 | |
PCT/US2006/006784 WO2006091917A2 (en) | 2005-02-24 | 2006-02-24 | Method for detection of faulty antenna array elements |
US11/659,772 US7583229B2 (en) | 2005-02-24 | 2006-02-24 | Method for detection of faulty antenna array elements |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140247182A1 (en) * | 2012-03-16 | 2014-09-04 | Rohde & Schwarz Gmbh & Co. Kg | Method, system and calibration target for the automatic calibration of an imaging antenna array |
US10135551B2 (en) | 2016-12-07 | 2018-11-20 | Qatar University | Method of identifying faulty antenna elements in massive uniform linear antenna arrays |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2978249B1 (en) * | 2011-07-22 | 2013-07-26 | Thales Sa | CALIBRATION AND TEST DEVICE FOR AN ACTIVE ANTENNA, IN PARTICULAR AN ADVANCED ANTENNA FOR AN AIRBORNE RADAR |
US10107844B2 (en) * | 2013-02-11 | 2018-10-23 | Telefonaktiebolaget Lm Ericsson (Publ) | Antennas with unique electronic signature |
DE102019121410A1 (en) * | 2019-08-08 | 2021-02-11 | Lisa Dräxlmaier GmbH | TEST DEVICE FOR TESTING AN ANTENNA |
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Also Published As
Publication number | Publication date |
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US20080094294A1 (en) | 2008-04-24 |
WO2006091917A3 (en) | 2007-05-03 |
WO2006091917A2 (en) | 2006-08-31 |
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